This invention concerns the measurement of the depth of a flowing liquid, and control of the flow rate of said liquid based upon a depth measurement.
Various methods and apparatus have been utilized to measure the depth of fluids under static and dynamic conditions. Such methods generally involve mechanical principles or the attenuation of a calibrated energy source such as electromagnetic waves, sound or radioactivity. When a calibrated energy source is employed, the energy is caused to pass through the liquid which absorbs the energy in an amount linearly proportional to the path length through the liquid. The intensity of the emergent energy is measured and compared to the intensity of the input energy, whereby the liquid path length is determined. In the case of the use of visible light directed through a liquid, the measurable interrelationships are governed by the classic Lambert's law equation: EQU log I/I.sub.e =kd
where I is the intensity of the light transmitted at a given wavelength, Io is the intensity of the incident light, d is the thickness through which the light is transmitted, and k is the extinction coefficient for the particular liquid and wavelength.
In most techniques which utilize transmission of a calibrated energy source through a fluid system, the transmission characteristics of the windows which permit entrance and exit of the energy with respect to the confined liquid are subject to uncertain variation due to sedimentation effects and other factors.
Methods and apparatus for measuring liquid depth are generally not suitable for measuring or controlling the flow rate of the liquid.
It is accordingly an object of the present invention to provide a method for measuring the depth of a flowing liquid by attenuation of a calibrated source of electromagnetic energy.
It is another object of this invention to provide a method and implementing apparatus for measuring the depth of a flowing liquid with lessened dependence upon the transmission characteristics of windows.
It is a further object of the present invention to provide a method and apparatus of the aforesaid nature for measuring the depth of a flowing liquid and controlling the flow rate of said liquid.
It is still another object of this invention to provide an improved apparatus of the aforesaid nature of simple and rugged construction which may be economically manufactured.
These objects and other objects and advantages of the invention will be apparent from the following description.